FDA approves Keytruda for triple-negative breast cancer subset
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The FDA granted accelerated approval to pembrolizumab combined with chemotherapy for treatment of patients with locally recurrent unresectable or metastatic triple-negative breast cancer whose tumors express PD-L1.
In addition, the FDA approved PD-L1 IHC 22C3 pharmDx (Dako North America, Inc.) as a companion diagnostic test for identifying patients with triple-negative breast cancer whose tumors express PD-L1 with a combined positive score (CPS) of 10 or higher.
The agency based the new indication for pembrolizumab (Keytruda, Merck), a PD-1 inhibitor, on results of the multicenter, double-blind, randomized, placebo-controlled, phase 3 KEYNOTE-355 trial, which included 847 patients with previously untreated, locally recurrent inoperable or metastatic disease whose tumors expressed PD-L1.
Researchers randomly assigned 566 patients to 200 mg pembrolizumab on day 1 every 3 weeks plus one of three chemotherapy regimens — nab-paclitaxel, paclitaxel or gemcitabine/carboplatin. All other patients (n = 281) received placebo plus chemotherapy.
The study met its primary endpoint of PFS among patients with a CPS of 10 or higher. In that group, researchers reported that the addition of pembrolizumab to chemotherapy significantly improved PFS (median, 9.7 months vs. 5.6 months; HR = 0.65; 95% CI, 0.49-0.86).
The most common treatment-related adverse events associated with the pembrolizumab chemotherapy regimen included fatigue, nausea, diarrhea, constipation, vomiting, alopecia, rash, cough, decreased appetite and headache.
The most common laboratory abnormalities that occurred among patients treated with pembrolizumab plus chemotherapy included anemia, leukopenia, neutropenia, lymphopenia, thrombocytopenia, elevated alanine transaminase and aspartate transaminase, hyperglycemia, hypoalbuminemia, increased alkaline phosphatase, hypocalcemia, hyponatremia, hypophosphatemia and hypokalemia.
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